Limits to Audible Alarm Signal Recognition when Encoding Alarm Context April, 2015

Transcription

1 Limits to Audible Alarm Signal Recognition when Encoding Alarm Context April, 2015 Peter Doyle, Sharon Allan, Shawn Sullivan, Adam Sapirstein and Maria Cvach

2 Audio Alarm Signals and Context Encoded a good degree of context in 17 different audio alarm signals 2 yrs. later assessed their discriminability Sources for the 17 signals included: Nurse call system Physiologic monitoring system Not vents or pumps Wireless phones Pagers 2

3 Discrimination Test Participants 25 CVSICU RNs, 3 levels experience No screening for hearing ability/loss Protocol One session recognition testing with 3 trials, each presenting17 tones randomly.wav files via headphones Each signal balanced for volume Each signal presented for 10 sec Responses recorded as correct/incorrect 3

4 Results: Recognition Accuracy Patient normal (Nurse call) 100% Voice call (WiFi phone) 100% Crisis (Monitor) 84% Code blue (Nurse call) 67% Code blue/lav emerg, etc. (WiFi phone) 67% Equipment disconnects/text msg (WiFi phone) 67% System warning (Monitor) 67% Advisory (Monitor) 65% Lav assist (Nurse call) 63% 4

5 Results Continued Crisis (Pager) 60% Non-crisis (Pager) 59% Warning (Monitor) 48% Equipment/vent alarm (Nurse call) 21% System advisory (Monitor) 15% Staff and Lav emerg (Nurse call) 13% Staff normal/equip disconnect (Nurse call) 3% Staff & Pt normal/lav assist (WiFi phone) 0% 5

6 Military-Standard-1472 Discriminable differences in intensity, pitch, beats and harmonics shall be provided. Audio warning signals should normally consist of two elements: and alerting signal and an identifying or action signal If absolute discrimination is required, the number of signals to be identified shall not exceed four 2 Not sustained 6

7 IEC Alarms should: Help determine urgency Locate the room/patient Determine or categorize the cause of the alarm condition Determine or categorize the nature of response or awareness required 7

8 ANSI/AAMI HE75:2009(R)2013 The goals that any alarm signal should meet include: Clearly communicate the appropriate degree of urgency Clearly identify the relevant location Clearly identify the reason for the alarm condition 8

9 Research Points Out People can only differentiate, learn, and/or remember a few different abstract auditory alarm signals (Stanton and Edworthy, 1999; Patterson, 1982). Medical professionals appear to be poor at correctly identifying auditory alarm signals in their environments. (Momtahan et al.,1993). Fewer than 30% of [non-anesthetist] participants could identify [16 melodic alarms designed per IEC Annex F with] 100% accuracy after practice. (Sanderson et.al.2006) 9

10 Summary of The Standards Discriminable differences shall be provided Absolute audible signals shall not exceed four Audible signals should help determine Urgency Location Categorize cause/reason for alarm condition Response required 10

11 What Now? Physiologists and clinicians decide on alarms levels and thresholds HF and engineers can assist with best use of technology within manufacturers constraints Reduce the number of signals/tones Ideally 3 tiers: Run / Walk / Shuffle Encode only the highest priority audible alarms with alarm-specific content Use other media (visual or voice) to convey context other than urgency 11

12 Tone Reduction Plan Reduce WiFi phone signals from 4 to 2 tiers of priority (eliminates 2 signal) Transfer physiologic monitor pager alarms to existing WiFi phone signals (eliminates 2 signal) Combine lav assist call with patient normal call (eliminates 1 signal) Disable the hall monitor crisis signals Retest 12

13 AAMI Alarm Foundation Efforts AAMI alarm standards committee recognizes the challenges AAMI supporting Judy Edworthy to develop 7-10 signals Those to be evaluated by an international work group International alarm committee to adopt a set of signals 13

14 References 1. ANSI/AAMI HE75: 2009, Human Factors Engineering- Design of Medical Devices 2. IEC General requirements, tests and guidance for alarm systems in medical electrical equipment and medical electrical systems 3. Military Standard 1472G, Department of Defense Design Criteria Standard, Human Engineering, 11 Jan Momtahan K, Hetu R, and Tansley B. Audibility and identification of auditory alarms in the operating room and intensive care unit. Ergonomics, 36: , Patterson RD. Guidelines for auditory warning systems on civil aircraft. Paper In: Civil Aviation Authority. London (U.K.): Civil Aviation Authority, Sanderson et. al. (Anaesthesia, 2006, 61, pages ) 7. Stanton N, and Edworthy J. Auditory warnings and displays: an overview. In: Stanton NA, and Edworthy J (Eds.).Human factors in auditory warnings. Brookfield (VT): Ashgate Publishing, 1999, pp